All things related to multicast

[Peter John Hill <>]

It sounds like you have a similar set up to us. We have two core 
switches (layer 2) that all of our routers are connected to. The two 
cores are in different subnets. Does this sound similar? First off... 
Make sure you are not doing IGMP snooping OR CGMP OR RGMP on your 
cores. You will most likely end up shooting yourself in the foot with 
it on. Maybe it can be done, I would have the most hope for IGMP 
snooping, but CGMP is definitely out. (at least in my experience)

Are you using anycast auto-rp? With that you can use sparse-mode pim on 
the routers. It is working for us. We have our two core routers acting 
as the anycast-rp.

Here is what we have configured:
on our cores:
ip multicast-routing
ip multicast multipath
!
interface Loopback0
 description Management Interface
 ip address 128.2.x.x 255.255.255.255
 ip pim sparse-mode
 ip sap listen
!
interface Loopback1
 description Anycast RP Interface
 ip address 128.2.z.z 255.255.255.255
 ip pim sparse-mode
!
interface Vlan1000
 ip pim sparse-mode
 ip igmp join-group 224.0.1.40
!
ip pim rp-address 128.2.1.130 30
ip pim accept-rp 128.2.1.130
ip pim accept-rp auto-rp
ip pim send-rp-announce Loopback0 scope 32 group-list 11
ip pim send-rp-discovery Loopback0 scope 32

The other core is set up very similarly. Both of them have the same 
configuration for Loopback1, the same exact (thus anycast) auto-rp 
address.

On our building routers we have:
ip multicast-routing
interface Vlan1000
 ip pim sparse-mode
! we also have a vlan 255 for our other core, it is also pim sparse-mode
!
ip pim rp-address 128.2.1.130 30
access-list 30 permit 224.0.1.39
access-list 30 permit 224.0.1.40
!
So, this is working for us. It took us a lot of work to get this going, 
but it is working now. We are seeing some issues (or have been but I 
have not checked lately) with one of the cores losing its msdp peering.

OH YES... IMPORTANT.
Our border router and our two cores are all MSDP peers with each other. 
This is how they are able to maintain the same multicast routing 
information. If you need help setting this up, please let me know.

If anyone sees anything that looks wrong, please let me know. It seems 
to be working, we can source and receive just fine. Good luck.

Peter Hill
Network Engineer
Carnegie Mellon Unversity

p.s. If you wan to set up a multicast beacon of your own, and need 
someone to join it, please let me know, and I can oblige.

On Friday, November 8, 2002, at 02:26  PM, Alan Crosswell wrote:

> Anybody have experience with this?  Is this what I want to use in lieu
> of the ability to do PIM snooping?  I have a dual-star L2 topology 
> using
> Catalyst 6509 switches which my routers are each connected to.  Right
> now I have IGMP snooping disabled on these switches since it seemed to
> interfere with multicast connectivity and didn't make sense since the
> only devices on the switch are routers so the only IGMP to snoop would 
> be
> router advertisements.
>
> Maybe I should just not touch anything.  It's sort of working today:-)
> /a

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